1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Watchdog driver for Broadcom BCM2835
4  *
5  * "bcm2708_wdog" driver written by Luke Diamand that was obtained from
6  * branch "rpi-3.6.y" of git://github.com/raspberrypi/linux.git was used
7  * as a hardware reference for the Broadcom BCM2835 watchdog timer.
8  *
9  * Copyright (C) 2013 Lubomir Rintel <lkundrak@v3.sk>
10  *
11  */
12 
13 #include <linux/delay.h>
14 #include <linux/types.h>
15 #include <linux/mfd/bcm2835-pm.h>
16 #include <linux/module.h>
17 #include <linux/io.h>
18 #include <linux/watchdog.h>
19 #include <linux/platform_device.h>
20 #include <linux/of_address.h>
21 #include <linux/of_platform.h>
22 
23 #define PM_RSTC				0x1c
24 #define PM_RSTS				0x20
25 #define PM_WDOG				0x24
26 
27 #define PM_PASSWORD			0x5a000000
28 
29 #define PM_WDOG_TIME_SET		0x000fffff
30 #define PM_RSTC_WRCFG_CLR		0xffffffcf
31 #define PM_RSTS_HADWRH_SET		0x00000040
32 #define PM_RSTC_WRCFG_SET		0x00000030
33 #define PM_RSTC_WRCFG_FULL_RESET	0x00000020
34 #define PM_RSTC_RESET			0x00000102
35 
36 /*
37  * The Raspberry Pi firmware uses the RSTS register to know which partition
38  * to boot from. The partition value is spread into bits 0, 2, 4, 6, 8, 10.
39  * Partition 63 is a special partition used by the firmware to indicate halt.
40  */
41 #define PM_RSTS_RASPBERRYPI_HALT	0x555
42 
43 #define SECS_TO_WDOG_TICKS(x) ((x) << 16)
44 #define WDOG_TICKS_TO_SECS(x) ((x) >> 16)
45 #define WDOG_TICKS_TO_MSECS(x) ((x) * 1000 >> 16)
46 
47 struct bcm2835_wdt {
48 	void __iomem		*base;
49 	spinlock_t		lock;
50 };
51 
52 static struct bcm2835_wdt *bcm2835_power_off_wdt;
53 
54 static unsigned int heartbeat;
55 static bool nowayout = WATCHDOG_NOWAYOUT;
56 
57 static bool bcm2835_wdt_is_running(struct bcm2835_wdt *wdt)
58 {
59 	uint32_t cur;
60 
61 	cur = readl(wdt->base + PM_RSTC);
62 
63 	return !!(cur & PM_RSTC_WRCFG_FULL_RESET);
64 }
65 
66 static int bcm2835_wdt_start(struct watchdog_device *wdog)
67 {
68 	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
69 	uint32_t cur;
70 	unsigned long flags;
71 
72 	spin_lock_irqsave(&wdt->lock, flags);
73 
74 	writel_relaxed(PM_PASSWORD | (SECS_TO_WDOG_TICKS(wdog->timeout) &
75 				PM_WDOG_TIME_SET), wdt->base + PM_WDOG);
76 	cur = readl_relaxed(wdt->base + PM_RSTC);
77 	writel_relaxed(PM_PASSWORD | (cur & PM_RSTC_WRCFG_CLR) |
78 		  PM_RSTC_WRCFG_FULL_RESET, wdt->base + PM_RSTC);
79 
80 	spin_unlock_irqrestore(&wdt->lock, flags);
81 
82 	return 0;
83 }
84 
85 static int bcm2835_wdt_stop(struct watchdog_device *wdog)
86 {
87 	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
88 
89 	writel_relaxed(PM_PASSWORD | PM_RSTC_RESET, wdt->base + PM_RSTC);
90 	return 0;
91 }
92 
93 static unsigned int bcm2835_wdt_get_timeleft(struct watchdog_device *wdog)
94 {
95 	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
96 
97 	uint32_t ret = readl_relaxed(wdt->base + PM_WDOG);
98 	return WDOG_TICKS_TO_SECS(ret & PM_WDOG_TIME_SET);
99 }
100 
101 static void __bcm2835_restart(struct bcm2835_wdt *wdt)
102 {
103 	u32 val;
104 
105 	/* use a timeout of 10 ticks (~150us) */
106 	writel_relaxed(10 | PM_PASSWORD, wdt->base + PM_WDOG);
107 	val = readl_relaxed(wdt->base + PM_RSTC);
108 	val &= PM_RSTC_WRCFG_CLR;
109 	val |= PM_PASSWORD | PM_RSTC_WRCFG_FULL_RESET;
110 	writel_relaxed(val, wdt->base + PM_RSTC);
111 
112 	/* No sleeping, possibly atomic. */
113 	mdelay(1);
114 }
115 
116 static int bcm2835_restart(struct watchdog_device *wdog,
117 			   unsigned long action, void *data)
118 {
119 	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
120 
121 	__bcm2835_restart(wdt);
122 
123 	return 0;
124 }
125 
126 static const struct watchdog_ops bcm2835_wdt_ops = {
127 	.owner =	THIS_MODULE,
128 	.start =	bcm2835_wdt_start,
129 	.stop =		bcm2835_wdt_stop,
130 	.get_timeleft =	bcm2835_wdt_get_timeleft,
131 	.restart =	bcm2835_restart,
132 };
133 
134 static const struct watchdog_info bcm2835_wdt_info = {
135 	.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
136 			WDIOF_KEEPALIVEPING,
137 	.identity =	"Broadcom BCM2835 Watchdog timer",
138 };
139 
140 static struct watchdog_device bcm2835_wdt_wdd = {
141 	.info =		&bcm2835_wdt_info,
142 	.ops =		&bcm2835_wdt_ops,
143 	.min_timeout =	1,
144 	.max_hw_heartbeat_ms =	WDOG_TICKS_TO_MSECS(PM_WDOG_TIME_SET),
145 	.timeout =	WDOG_TICKS_TO_SECS(PM_WDOG_TIME_SET),
146 };
147 
148 /*
149  * We can't really power off, but if we do the normal reset scheme, and
150  * indicate to bootcode.bin not to reboot, then most of the chip will be
151  * powered off.
152  */
153 static void bcm2835_power_off(void)
154 {
155 	struct bcm2835_wdt *wdt = bcm2835_power_off_wdt;
156 	u32 val;
157 
158 	/*
159 	 * We set the watchdog hard reset bit here to distinguish this reset
160 	 * from the normal (full) reset. bootcode.bin will not reboot after a
161 	 * hard reset.
162 	 */
163 	val = readl_relaxed(wdt->base + PM_RSTS);
164 	val |= PM_PASSWORD | PM_RSTS_RASPBERRYPI_HALT;
165 	writel_relaxed(val, wdt->base + PM_RSTS);
166 
167 	/* Continue with normal reset mechanism */
168 	__bcm2835_restart(wdt);
169 }
170 
171 static int bcm2835_wdt_probe(struct platform_device *pdev)
172 {
173 	struct bcm2835_pm *pm = dev_get_drvdata(pdev->dev.parent);
174 	struct device *dev = &pdev->dev;
175 	struct bcm2835_wdt *wdt;
176 	int err;
177 
178 	wdt = devm_kzalloc(dev, sizeof(struct bcm2835_wdt), GFP_KERNEL);
179 	if (!wdt)
180 		return -ENOMEM;
181 
182 	spin_lock_init(&wdt->lock);
183 
184 	wdt->base = pm->base;
185 
186 	watchdog_set_drvdata(&bcm2835_wdt_wdd, wdt);
187 	watchdog_init_timeout(&bcm2835_wdt_wdd, heartbeat, dev);
188 	watchdog_set_nowayout(&bcm2835_wdt_wdd, nowayout);
189 	bcm2835_wdt_wdd.parent = dev;
190 	if (bcm2835_wdt_is_running(wdt)) {
191 		/*
192 		 * The currently active timeout value (set by the
193 		 * bootloader) may be different from the module
194 		 * heartbeat parameter or the value in device
195 		 * tree. But we just need to set WDOG_HW_RUNNING,
196 		 * because then the framework will "immediately" ping
197 		 * the device, updating the timeout.
198 		 */
199 		set_bit(WDOG_HW_RUNNING, &bcm2835_wdt_wdd.status);
200 	}
201 
202 	watchdog_set_restart_priority(&bcm2835_wdt_wdd, 128);
203 
204 	watchdog_stop_on_reboot(&bcm2835_wdt_wdd);
205 	err = devm_watchdog_register_device(dev, &bcm2835_wdt_wdd);
206 	if (err)
207 		return err;
208 
209 	if (of_device_is_system_power_controller(pdev->dev.parent->of_node)) {
210 		if (!pm_power_off) {
211 			pm_power_off = bcm2835_power_off;
212 			bcm2835_power_off_wdt = wdt;
213 		} else {
214 			dev_info(dev, "Poweroff handler already present!\n");
215 		}
216 	}
217 
218 	dev_info(dev, "Broadcom BCM2835 watchdog timer");
219 	return 0;
220 }
221 
222 static void bcm2835_wdt_remove(struct platform_device *pdev)
223 {
224 	if (pm_power_off == bcm2835_power_off)
225 		pm_power_off = NULL;
226 }
227 
228 static struct platform_driver bcm2835_wdt_driver = {
229 	.probe		= bcm2835_wdt_probe,
230 	.remove_new	= bcm2835_wdt_remove,
231 	.driver = {
232 		.name =		"bcm2835-wdt",
233 	},
234 };
235 module_platform_driver(bcm2835_wdt_driver);
236 
237 module_param(heartbeat, uint, 0);
238 MODULE_PARM_DESC(heartbeat, "Initial watchdog heartbeat in seconds");
239 
240 module_param(nowayout, bool, 0);
241 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
242 				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
243 
244 MODULE_ALIAS("platform:bcm2835-wdt");
245 MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
246 MODULE_DESCRIPTION("Driver for Broadcom BCM2835 watchdog timer");
247 MODULE_LICENSE("GPL");
248